Combined linear motion potentiometer and switch



COMBINED LINEAR MOTION POTENTIOMETERAND SWITCH Filed Jan. 4, 1968 Feb.24, 1970 E- PFEUFER 2 Sheets-Sheet l I NVEN TOR 5444 PFEl/FEPATTORNEY-5.

E. A. PFEUFER 3,497,857

2 Sheets-Sheet 2 m m me v m w B W WA 1 %N 1 E NT w m M v 1 m J m f W w 5m WAN I 1 mw mm q m A wm m: a NM. WI \Mm. A..- F W v i. NH .1. m. A? \lr L A/wAA/An Feb. 24, 1970 COMBINED LINEAR MOTION POTENTIOMETER ANDSWITCH Filed Jan. 4, 1968 United States Patent 3,497,857 COMBINED LINEARMOTION POTENTIOMETER AND SWITCH Earl A. Pfeufer, St. Marys, Pa.,assignor to Stackpole Carbon Company, St. Marys, Pa., a corporation ofPennsylvania Filed Jan. 4, 1968, Ser. No. 695,647 Int. Cl. H01c /08 US.Cl. 338178 6 Claims ABSTRACT OF THE DISCLOSURE A resistance strip and acollector strip are mounted opposite each other in a housing and areengaged by a bridging contact between them carried by an insulatingslide. A switch spring contact strip is disposed between the other twostrips at one edge thereof and has a free end normally engaging a fixedcontact. The spring contact strip has a portion near the fixed contactin the path of the inner end of the slide for engagement thereby tospring the contact strip away from the fixed contact when the slide isat that end of the housing.

It is among the objects of this invention to provide a combined linearmotion potentiometer and switch, in which the member that moves thebridging contact also operates the switch, which is simple andinexpensive in construction, which has a minimum of parts, which can beassembled quickly and which is compact and durable.

In accordance with this invention an elongated housing has a front andback wall connected by parallel side walls. A resistance strip isdisposed inside the housing along one side wall, and a collector stripis disposed inside the housing along the other side wall. The front ofthe housing is provided with a central longitudinal slot, in which aslide is mounted for movement lengthwise of the housing. The slideextends inwardly across the strips and carries a bridging contact inengagement with them.

Between the two strips there is a switch spring contact strip thatextends along the inner surface of the back of the housing and has astationary end. The opposite or free end of the contact strip normallyengages a fixed contact mounted in the housing between the contact stripand the front wall of the housing. The contact strip also has a portionnear the fixed contact disposed in the path of the inner end of theslide for engagement by it in order to spring the contact strip awayfrom the fixed contact when the slide is at that end of the housing.

The preferred embodiment of the invention is illustrated in theaccompanying drawings, in which:

FIG. 1 is a side' view, with a piece of the rear wall broken away;

FIG. 2 is an inside view of half of the unit, with the switch open;

FIG. 3 is a longitudinal section taken on the line III-III of FIG. 1;and

FIG. 4 is a cross section taken on the line IVIV of FG. 1.

Referring to the drawings, the elongated rectangular housing 1 of thepotentiometer may be formed of a molded plastic or other suitable rigidmaterial. The top or front wall of the housing is provided with acentral longitudinal slot 2 through it extending nearly the full lengthof the housing. The housing preferably is made from two molded halfsections that have meeting edges extending from front to back across theend walls of the housing and lengthwise along its bottom or back wall.The meeting edges of the two molded half sections may be joined togetherin any suitable manner, such as by a spring clip 3 snapped into recess 4in the back and side walls of the two sections.

Each of the meeting edges of the half sections is provided with notches6 and tongues 7. The tongues on each half section fit in the notches inthe other half section so that the two sections interlock with eachother. The tongues are shorter than the notches so that rectangularopenings are left at the outer end of the tongues for a purpose to bedescribed. A shallow opening 9 extends through each end wall of thehousing at the same level as the adjoining inner surface of the backwall. This opening is formed partly in each half section of the hous-1ng.

Disposed inside the housing, flat against one side wall, is a straightflat strip 11 to which electric resistance material has been applied.Electric terminals 12 are connected to opposite ends of the strip andextend out of the housing. The terminals may take various forms, butpreferably each is formed from a narrow flat metal strip that has aspring tongue 13 struck out of its inner end portion. As shown in FIG.4, this tongue and the opposed portion of the terminal straddle andtightly clamp the resistance element between them. The terminal extendsout of the housing through one of the openings in its back wall and haslateral projections that engage the outer surface of that wall toprevent the terminal from being pushed into the housing.

Disposed fiat against the inner surface of the other side of the housingis a metal collector strip 15, which is provided near one end with anintegral terminal 16 that extends out through an opening in the backwall of the housing. The same end of the collector strip is providedwith an ear 17 projecting into an opening 16 in the adjacent end of thehousing. There is no problem in assembling the strips and terminals withthe housing, because it is done before the two half sections of thehousing are joined together.

Movable lengthwise of the housing is a slide 20 made of insulatingmaterial and the opposite sides of which are provided with parallellongitudinal grooves 21 that receive the side walls of the slot 2 in thefront of the housing, whereby the slide is locked in the housing but canbe moved back and forth along the slot. The slide has actuating knob 22that projects from the housing. The slide extends inwardly across theresistance and collector strips, from both of which it is spaced. Thisinner portion of the slide carries a bridging contact 23 that engagesboth strips to electrically connect them. One way of making the innerportion of the slide is in the form of a rectangular frame 24, in whicha flexible metal coil is carried. The coil projects from opposite sidesof the frame and is compressed laterally slightly by the two strips thatit engages. Each of the two strips that the wire coil presses againstwill be slidingly engaged by each convolution of the coil, therebyproviding a multiplicity of contacts with each strip.

It is a feature of this invention that the housing also contains anelectrical switch that is operated by the slide. Accordingly, a metalspring contact strip 26 extends along the inner surface of the back wallof the housing between the resistance strip and the collector strip. Oneend portion of the contact strip extends out through opening 9 in theadjoining end of the housing and then is bent at right angles to form arearwardly projecting electric terminal 28. The contact strip fitstightly in the slot, which thereby anchors that end of the strip. Theopposite or free end of the strip is at the opposite end of the housing.It is highly desirable to provide the inside of the back wall of thehousing with a pair of laterally spaced ledges 29 that are integral withit and with the side walls also, as shown in FIG. 4. These ledges stopshort of the terminals that extend out of the back of the housing. Theledge space the resistance and the collector strips from the backwalland provide a groove between them, in which the contact strip isdisposed. The two ledges therefore prevent any lateral movement of thecontact strip that otherwise might occur if its free end were free toswing laterally by causing the opposite end to prevent sliding in theend wall slot.

As shown in FIGS. 1 and 2, the free end of the contact strip 26 is bentto extend toward the front of the housing and then is bent out towardthe adjacent end wall to form a fiat contact 31. Between this contactand the front wall there is a fixed contact 32 that extends laterally,as shown in FIGS. 3 and 4, toward the sidewall of the housing alongwhich the collector strip extends. The adjacent end of thecollector'strip is spaced far enough from the end of the housing toprovide room for the inner end of a terminal 33 integrally connectedwith the fixed contact and extending out through a slot 6 in the endwall. Outside the housing the terminal makes a right angle turn andextends rearwardly parallel to the other terminals. The inner end ofterminal 33 preferably has an integral extension 34 that engages fiatagainst the side wall of the housing and extends in back of as well asin front of the fixed contact to help steady it. The spring contact 31engages the fixed contact to maintain the switch closed as long as theslide is not at that end of the housing, as shown in FIG. 1. Aconsiderable length of the spring contact strip 26, extending inwardlyfrom its free end, is spaced from the back wall of the housing While theswitch is closed. To avoid any possibility of the switch not closing, asuitable slightly compressed resilient or spring device may be mountedbetween contact 26 and the back wall of the housing to urge the contacttoward fixed contact 32. A tiny block of sponge rubber, for example, canbe used for this purpose.

To open the switch, the slide is moved toward the fixed contact. Justbefore it reaches that contactit engages a portion of the contact stripin its path and springs the free end of the strip away from the fixedcontact as shown in FIG. 2. The portion of the contact strip thusengaged preferably is a hump 36 that is formed in the strip close to itsfree end. The inner end of the slide engages this hump and slides ontoit, thereby pushing the free end of the strip toward the back wall ofthe housing and opening the switch to take the resistance strip out ofthe circuit. As soon as the slide moves lengthwise of the housing awayfrom the hump, the contact strip moves forward and engages the fixedcontact again. The value of the resistance at any given time depends onthe location of the slide lengthwise of the housing. To help hold theslide in its switch-opening position, and also to give the operator thefeeling" that the slide has opened the switch, the inner end of frame 24may be provided with a notch 37 that will receive hump 36. A similarnotch 38 at the other side of the frame will serve the same purpose ifthe slide is reversed when inserted in the housing, thereby making itunnecessary to insert the slide in any particular way.

According to the provisions of the patent statutes, I have explained theprinciple of my invention and have illustrated and described what I nowconsider to represent its best embodiment. However, I desire to have itunderstood that, within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically illustrated anddescribed.

' I claim: 1. A combined linear motion potentiometer and.switch,comprising an elongated housing having front and back walls connected byparallelside walls, a resistance strip disposed inside the housing alongone side wall, electric terminals engaging the opposite ends of thestrip, a collector strip disposed inside the housing along the otherside wall and provided with a terminaLthe front of the housing beingprovided with a central longitudinal slot therethrough, a slide mountedin said slot and movable lengthwise thereof, the slide extendinginwardly across said strips and spaced from both, a bridging contactcarried by the slide in engagement with both strips, a-switch springcontact strip extending along the inner surface of said back wallbetween said resistance and collector strips and having a stationary endand a free end, a terminal connected with said stationary end of thecontact strip adjacent one end of the housing, a fixed contact mountedin the opposite end of the housing between said free'end of the contactstrip and the front wall of the housing, a length of the contact stripadjacent the fixed contact normally being spaced from said back wall tohold said free end against the fixed contact, and a terminal connectedwith the fixed contact, the spring contact strip having a portion nearthe 'fixed contact in the path of the inner end of the longitudinallymovable slide for engagement thereby to spring the contact strip awayfrom the fixed contact when the slide is at that end of said housing.

2. A combined linear motion potentiometer and switch according to claim1, in which said spring contact strip portion is a reversely bent humpin the contact strip.

3. A combined linear motion potentiometer and switch according to claim1, in which all of said terminals extend rearwardly away from saidhousing.

4. A combined linear motion potentiometer and switch according to claim1, in which the switch terminals extend out of the opposite ends of thehousing and then rearwardly, and said resistance andcollector terminalsextend through the back wall of the housing.

5. A combined linear motion potentiometer and switch according to claim1, in which said fixed contact extends part way across the housing fromsaid other side wall from a point between the collector strip andadjacent end of the housing, and said last-mentioned terminal extendsthrough said adjacent end of the housing and is integrally connected tothe fixed contact beside said other side wall.

6. A combined linear motion potentiometer and switch according to claim2, in which the inner end of the slide is provided with a notch forreceiving said hump when the switch is open.

References Cited UNITED STATES PATENTS 3,389,365 6/1968 Matthews et al33820O 3,375,446 3/1968 Guyton 338l98 X 2,457,095 12/ 1948 Strother338-200 X LARAMIE E. ASKIN, Primary Examiner A. T. GRIMLEY, AssistantExaminer US. Cl. X.R.

ZOO- 166; 338-198

